U.S. patent number 6,098,823 [Application Number 09/031,272] was granted by the patent office on 2000-08-08 for stabilizing arrangements in and for load-bearing apparatus.
This patent grant is currently assigned to JLG Industries, Inc.. Invention is credited to Mohamed Yahiaoui.
United States Patent |
6,098,823 |
Yahiaoui |
August 8, 2000 |
**Please see images for:
( Certificate of Correction ) ** |
Stabilizing arrangements in and for load-bearing apparatus
Abstract
An arrangement in or for a boom lift or other type of lift or
load-bearing apparatus, in which a stabilizing moment is imparted
based on at least one state of at least a portion of the boom or
other portion of the lift or load-bearing apparatus. Also
contemplated is an arrangement for redistributing mass
responsively, based on at least one state of at least a portion of
a load-bearing apparatus.
Inventors: |
Yahiaoui; Mohamed (Hagerstown,
MD) |
Assignee: |
JLG Industries, Inc.
(McConnellsburg, PA)
|
Family
ID: |
21858543 |
Appl.
No.: |
09/031,272 |
Filed: |
February 27, 1998 |
Current U.S.
Class: |
212/197; 182/2.9;
212/279 |
Current CPC
Class: |
B66F
11/044 (20130101) |
Current International
Class: |
B66F
11/04 (20060101); B66C 023/76 () |
Field of
Search: |
;212/195,198,196,279,256,197 ;162/2.9,7.11 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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38376 |
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Jan 1936 |
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NL |
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205245 |
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Jan 1968 |
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SU |
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1225805 |
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Apr 1986 |
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SU |
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1539162 |
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Jan 1990 |
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SU |
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Primary Examiner: Brahan; Thomas J.
Attorney, Agent or Firm: Reed Smith Shaw & McClay
LLP
Claims
What is claimed is:
1. Load-bearing apparatus comprising:
a reference portion;
an arm support portion;
a pivot mount disposed on said arm support portion;
a load-bearing arm being pivotably mounted on said arm support
portion at said pivot mount;
said arm support portion being translatable with respect to said
reference portion; and
a motion linking arrangement for linking motion of said arm support
portion with motion of said load-bearing arm;
said motion linking arrangement being adapted to simultaneously
translate said arm support portion, said pivot mount and said
load-bearing arm with respect to said reference portion in response
to motion of said load-bearing arm and in accordance with a
predetermined algorithm that governs the simultaneous translation
of said arm support portion, said pivot mount and said load-bearing
arm in response to motion of said load-bearing arm, whereby:
a stabilizing moment is imparted to said apparatus as motion of
said load-bearing arm causes said apparatus to
approach a position of critical backward instability; and
a stabilizing moment is imparted to said apparatus a motion of said
load-bearing arm causes said apparatus do approach a position of
critical forward instability.
2. The apparatus according to claim 1, wherein said motion linking
arrangement comprises a mechanical operational connection between
said load-bearing arm and said reference portion.
3. The apparatus according to claim 2, wherein said mechanical
operational connection comprises a discrete mechanics link between
said load-bearing arm and said reference portion.
4. The apparatus according to claim 1, wherein said motion linking
arrangement comprises a non-mechanical operational connection
between said arm support portion and said reference portion.
5. The apparatus according to claim 1, wherein said motion linking
arrangement comprises a hybrid mechanical and non-mechanical
operational connection between said arm support portion and said
reference portion.
6. The apparatus according to claim 1, wherein said motion linking
arrangement is adapted to simultaneously translate said arm support
portion, said pivot mount and said load-bearing arm with respect to
said reference portion at least as a function of a vertical angle
of said load-bearing arm.
7. The apparatus according to claim 1, wherein said motion linking
arrangement is adapted to simultaneously translate said arm support
portion, said pivot mount and said load-bearing arm with respect to
said reference portion at least as a function of a telescoping
length of said load-bearing arm.
8. The apparatus according to claim 1, wherein said motion linking
arrangement is adapted to simultaneously translate said arm support
portion, said pivot mount and said load-bearing arm with respect to
said reference portion at least as a function of a vertical angle
and a telescoping length of said load-bearing arm.
9. The apparatus according to claim 1, wherein said load-bearing
apparatus is a boom lift.
10. The apparatus according to claim 1, further comprising:
a turntable for positioning said load-bearing arm at a
predetermined swing angle; and
said turntable comprising said reference portion and said arm
support portion.
Description
FIELD OF THE INVENTION
The present invention generally relates to lift structures and/or
load-bearing vehicles.
BACKGROUND OF THE INVENTION
Historically, there have been developed a wide range of lift
structures that are arranged in such a manner as to elevate
personnel or material in order to provide facilitated access to an
elevated location.
Different types of lifts vary in size, shape and function. For
example, "vertical pole" lifts generally involve the use of a
telescoping mast or sequentially extending mast (in which mast
segments are usually "stacked" along a horizontal direction and
then propagate upwardly one-by-one), on which is mounted a basket,
cage or other platform structure intended to carry one or more
individuals. Most "vertical pole" lifts are intended to carry only
one individual, however, and are generally designed to elevate
solely in a vertical direction. U.S. Pat. No. 3,752,261 (Bushnell,
Jr.), U.S. Pat. No. 4,657,112 (Ream et al.) and U.S. Pat. No.
4,015,686 (Bushnell, Jr.) disclose general examples of such
lifts.
"Scissors lifts", on the other hand, involve the use of a
scissors-type mechanism for propagating a basket, cage or platform
upwardly. Again, the propagation is solely along a generally
vertical direction, but in this case the more rigid structure of
the scissors mechanism permits greater loads to be propagated and
carried. U.S. Pat. No. 5,390,760 (Murphy) and U.S. Pat. No.
3,817,846 (Wehmeyer) disclose general examples of such lifts.
"Boom lifts" involve the use of a pivotable, and often extendible,
boom structure to propagate a basket, cage or platform both
upwardly and in a variety of other directions. U.S. Pat. No.
3,861,498 (Grove) and Re. 31,400 (Rallis, et al.) disclose general
examples of such lifts.
Other types of lifts, not typically falling into one of the three
categories outlined above, can also be used for similar purposes,
that is, for propagating personnel or material in a generally
upward direction to access an elevated workspace. U.S. Pat. Nos.
4,488,326 (Cherry), U.S. Pat. No. 3,927,732 (Ooka et al.), U.S.
Pat. No. 5,299,653 (Nebel), U.S. Pat. No. 4,154,318 (Malleone),
U.S. Pat. No. 4,799,848 (Buckley) and U.S. Pat. No. 4,147,263
(Frederick et al.) disclose general examples of lifts outside of
the three categories discussed above.
Many types of vehicles and lift structures, especially boom lifts,
excavators, cranes, backhoes, and other similar machines, have
centers of mass that migrate significantly during use. In contrast,
automobiles and similar vehicles have their lateral centers of mass
located at some point substantially along the longitudinal axes
thereof and these tend not to migrate significantly at all. Thus, a
migrating center of mass has been a perennial problem with certain
vehicles or machines, including boom lifts.
In the instant disclosure, the terms "boom" and "load-bearing arm"
may each be taken to be indicative of essentially any device or
instrument that provides extended reach, either for the purpose of
moving personnel for doing work, for or moving goods, or both.
Thus, in the instant application, the term "boom" not only can be
taken to be indicative of a telescoping and/or articulated boom in
a boom lift, but might also include those types of mechanical
extensions found in essentially any of the equipment described or
referred to herein, such as, for example, excavators, cranes,
backhoes, tree harvesters, mechanical pincers and other similar
machines.
Throughout the instant disclosure, reference will also be made to
the angle that a boom or lower portion of a boom (e.g., a base boom
of a straight [telescopic] boom lift or a tower boom of an
articulated boom lift) forms with the horizontal. Conventionally,
this is often termed the "lift angle", "vertical angle" or
"elevation angle". Each of these terms may be considered to be
interchangeable with respect to one another.
As a boom is extended and a load is applied to the platform or
bucket thereof, the vehicle or lift structure's center of mass
moves outwardly toward the supporting wheels, tracks, outriggers or
other supporting elements being used. If a sufficient load is
applied to the boom, the center of mass will move beyond the wheels
or other supporting elements and the vehicle lift will tip over.
The imaginary line along a support surface (e.g., the ground) about
which a vehicle tips is known as the "tipline". A more detailed
discussion of the principles of tipping is provided in copending
and commonly assigned U.S. patent application Ser. No. 08/890,863,
which is hereby incorporated by reference as if set forth in its
entirety herein.
By defining the tipline of a lift or vehicle as near to the
perimeter of the lift or vehicle's chassis as possible, the
stability of the lift or vehicle is increased. This increase in
stability permits the lift or vehicle to perform its intended
function with the minimum amount of necessary counterbalance
weight, which results in lower costs, improved flotation on soft
surfaces, easier transport, etc.
In the context of booms, two types of stability are generally
addressed, namely "forward" and "backward" stability. "Forward"
stability refers to that type of stability addressed when a boom is
positioned in a maximally forward position. In most cases, this
will result in the boom being substantially horizontal. On the
other hand, "backward" stability refers to that type of stability
addressed when a boom is positioned in a maximally backward
position (at least in terms of the lift angle). In most cases, this
will result in the boom being close to vertical, if not completely
so.
Typically, not only can a boom be displaced (i.e., pivoted) through
a vertical plane, but also through a horizontal plane. In a boom
lift, for example, the horizontal positioning is usually effected
via a turntable that supports the boom. The turntable, and all
components propelled by it (including the boom and work platform),
are often termed the "superstructure". As the wheeled chassis found
in typical lift arrangements will usually not exhibit complete
circumferential symmetry of mass, it will be appreciated that there
exist certain circumferential positions of the boom that are more
likely to lend themselves to potential instability than others.
Thus, in the case of a lift in which the chassis or other main
frame does not exhibit symmetry of mass with regard to all possible
circumferential positions of the boom, then a greater potential for
instability will exist, for example, along a lateral direction of
the chassis or main frame, that is, in a direction that is
orthogonal to the longitudinal lie of the chassis or main frame
(assuming that the "longitudinal" dimension of the chassis or main
frame is defined as being longer than the "lateral" dimension of
the chassis or main frame). Thus, when incorporating safety
requirements into the lift, these circumferential positions of
maximum potential instability must be taken into account.
Throughout the instant disclosure, reference will often be made to
the circumferential position assumed by a boom or a main boom
portion (e.g., a base boom of a straight [telescopic] boom lift or
a tower boom and an articulated boom lift). This circumferential
position is often referred to as the "swing" or "slew" of the boom,
but may also be referred to as the "horizontal angle" or
"circumferential angle" of the boom. All of these terms may be
considered to be interchangeable with one another.
Historically, it has been the norm to ensure the presence of a
counterweight to the boom. In this manner, when the boom is in a
maximally forward position, the counterweight will help counteract
the destabilizing moment contributed to by the boom (with personnel
or material load).
In theory, a counterweight may involve any component or components
that, when situated appropriately with respect to the boom, serve
to counterbalance the boom. In practice, it has been quite common
to provide a dedicated counterweight that is an integral portion of
the turntable structure. However, it is possible to use any of
several components either as a singular counterweight or as part of
a composite counterweight. Such components include, but are not
limited to, the turntable itself, a shell disposed about the
turntable, an engine disposed within the vehicle chassis, or other
relatively massive components that simultaneously form a
functioning part of the chassis or turntable. It is to be
understood that, throughout this disclosure, "counterweight" can be
taken to mean either a dedicated object specifically provided for
the purpose of counterbalancing a boom and essentially serving no
other purpose, or other objects such as those just described, or
any combination of items from both of these categories.
The use of a counterweight does have somewhat of an opposite
consequence, however, when one considers the issue of backward
instability. Particularly, when a boom is moved into a maximally
backward position, it will be appreciated that a destabilizing
moment, contributed to by the boom (with personnel or material
load) and counterweight, could act in a backward direction. On the
other hand, if a destabilizing moment is not present, even a small
net stabilizing moment might be undesirable. Thus, it has been the
norm to accord the chassis or other main frame an even greater
weight than might be desired, for the purpose of counterbalancing
the destabilizing moment that contributes to backward
instability.
Although the measures described hereinabove have conventionally
been sufficient to reduce the risk of tipping in either a forward
or a backward direction, concern has arisen in the industry over
the costs associated with providing an overly massive chassis or
frame. The mass of a chassis or frame not only has ramifications in
manufacturing costs, but also in transport costs or in other
factors, such as the load that might be applied to fragile surfaces
(e.g., mud or sand). Accordingly, a need has been recognized in
conjunction with keeping such additional mass to a minimum.
At times, however, concerns over the mass of a chassis or frame
might be overridden by concerns over the work envelope, or reach,
of the load-bearing apparatus in question. In such instances, a
need has been recognized in conjunction with increasing the
available work envelope, or reach, of a load-bearing apparatus, for
a given mass of the apparatus.
A need has additionally been recognized in conjunction with
optimizing a load-bearing apparatus so as to provide a reduced
weight and increased work envelope, or reach, deemed appropriate
for the intended tasks to be performed by the load-bearing
apparatus.
Some previous efforts have attempted to reduce the likelihood of
tipping via one or more movable portions of the vehicle or machine
in question. For example, U.S. Pat. No. 3,768,665, to Eiler et al.,
appears to disclose a mobile crane with a jib mounted on a
rotatable element and a counterweight connected to an inner end of
the jib by connecting links. It is also disclosed that, to avoid
tipping of the vehicle, the jib and the counterweight can be moved
to fore and aft positions. However, the movement of the
counterweight is completely independent of any other factors, such
as the position of the jib.
Some previous efforts involve the translation of boom structures in
a single direction, but only for the purpose of repositioning the
boom structure to alter the available "work envelope", or the reach
afforded by the boom structure. Generally, such efforts have
resulted in structures that might involve undesirable
inefficiencies of movement or adjustment, or might be limited in
their capabilities.
In this regard, U.S. Pat. No. 4,147,263, to Frederick et al.,
involves a high lift loader that permits longitudinal repositioning
of the telescoping structure. However, the repositioning is
one-dimensional in nature and is completely independent of any
other physical parameters of the machine (e.g. a physical state of
the boom).
In an apparent effort to facilitate upward travel in a lift, U.S.
Pat. No. 4,070,807, to Smith, Jr. appears to disclose an
arrangement for ensuring that a personnel bucket travels
substantially in a vertical line (e.g. along a wall), irrespective
of the orientation of the boom structure supporting it. In this
way, a continual adjustment is made, responsive to the effective
vertical angle of the boom structure, to push the bucket outwardly
or inwardly so that, instead of describing an arc as would normally
be expected, it follows nearly a straight line on the way up or
down.
As part of this effort, a portion of the device is capable of
sliding, but only in a horizontal direction corresponding to the
longitudinal direction of the lift. However, there is no teaching
or suggestion that this action could or should be part of an effort
to compensate for any destabilizing moments, and for this reason
the range of movement of the boom structure might be highly
limited. Furthermore, the objective of maintaining substantially
straight-line travel might come at the expense of actually reducing
the work envelope (i.e., available reach) of the boom.
SUMMARY OF THE INVENTION
Generally, at least one presently preferred embodiment of the
present invention broadly contemplates load-bearing apparatus
comprising: a load-bearing arm; and an arrangement for imparting to
the apparatus a stabilizing moment based on at least one state of
at least a portion of the load-bearing arm.
Further, at least one presently preferred embodiment of the present
invention broadly contemplates a boom lift comprising: a boom; and
an arrangement for imparting to the boom lift a stabilizing moment
based on at least one state of at least a portion of the boom.
Additionally, at least one presently preferred embodiment of the
present invention broadly contemplates load-bearing apparatus
comprising: a load-bearing portion; and an arrangement for
imparting to the load-bearing apparatus a stabilizing force, based
on at least one state of the load-bearing portion.
Further, at least one presently preferred embodiment of the present
invention broadly contemplates load-bearing apparatus comprising an
arrangement for responsively redistributing mass based on at least
one state of at least a portion of the load-bearing apparatus.
Finally, but not necessarily exclusively, at least one presently
preferred embodiment of the present invention broadly contemplates
load-bearing apparatus comprising: a load-bearing arm; an
arrangement for supporting said load-bearing apparatus on a
surface; and an arrangement for imparting to the apparatus a
reduction in structural loading as experienced at the interface
between the supporting arrangement and the surface on which the
load-bearing apparatus is supported.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention and its presently preferred embodiments will
be better understood by way of reference to the detailed disclosure
herebelow and to the accompanying drawings, wherein:
FIG. 1 is a schematic elevational representation of a lift
structure and associated components;
FIG. 2a is essentially the same view as FIG. 1, illustrating the
boom of the lift structure in a vertically intermediate
position;
FIG. 2b is essentially the same view as FIG. 1, illustrating the
boom of the lift structure in a significantly lowered position;
FIG. 2c is essentially the same view as FIG. 1, illustrating the
boom of the lift structure in a significantly raised position;
FIG. 3 is a schematic elevational representation of a lift
structure, and associated components, according to at least one
preferred embodiment of the present invention;
FIG. 4a is essentially the same view as FIG. 3, illustrating the
boom of the lift structure in a vertically intermediate
position;
FIG. 4b is essentially the same view as FIG. 3, illustrating the
boom of the lift structure in a significantly lowered position;
FIG. 4c is essentially the same view as FIG. 3, illustrating the
boom of the lift structure in a significantly raised position;
FIG. 5 is a perspective representation of selected components of a
boom lift according to at least one preferred embodiment of the
present invention;
FIG. 6 is a side elevational representation of essentially the same
boom lift as illustrated in FIG. 5, illustrating a boom portion in
a significantly lowered position;
FIG. 7 is essentially the same view as FIG. 6, illustrating a boom
portion in a significantly raised position; and
FIG. 8 illustrates an alternative embodiment of the present
invention, in which electronic feedback is utilized to control the
positioning of a movable turntable portion.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Throughout the instant disclosure, it will be appreciated that
several terms may be used interchangeably with one another, some of
which are briefly discussed immediately below.
The terms "basket", "cage", "platform", "work platform", "working
platform", "platform structure", "bucket" and "carriage" are all
indicative of portions of a lift structure on or in which one or
more individuals, or a load of material, may be positioned so as to
be raised to an elevated location. It is to be understood that the
occurrence of any of these terms singly can be taken to indicate
the interchangeability therewith of any of the other terms.
The terms "slide" and "translate", and their verbal conjugations
(e.g., "sliding", "slideable", "translating", etc.), as employed
herein, are interchangeable and are indicative of a strictly
translational type of movement undertaken by a given component or
components.
FIGS. 1-4c are schematic representations of boom lifts that are
intended to convey some basic concepts relating to the prior art
and to at least one embodiment of the present invention. As such,
it is to be understood that FIGS. 1-4c are not necessarily to scale
and that the dimensions, proportions and positional relationships
illustrated therein might be exaggerated or diminished simply to
assist in illustrating such basic concepts.
FIG. 1 schematically illustrates a typical boom lift 100 that might
employ the present invention in accordance with at least one
presently preferred embodiment. As is known conventionally, a
chassis 102 is supported on wheels 104. Conceivable substitutes for
wheels 104 might be tracks (similar to the type found in a military
tank), skids, outriggers or other types of fixed or movable support
arrangements. A boom 106, extending from turntable 108, will
preferably support at its outer end a platform 110. Turntable 108
may preferably be configured to effect a horizontal pivoting
motion, as indicated by the arrows, in order to selectively
position the boom 106 at any of a number of circumferential
positions lying along a horizontal plane. There is preferably a
drive arrangement 112 (such as a slew or swing drive) to effect the
aforementioned horizontal pivoting motion. On the other hand, there
is also preferably provided a drive arrangement 114 (such as a lift
cylinder) for pivoting the boom 106 along a generally vertical
plane, to establish the position of boom 106 at a desired vertical
angle a. The drive arrangements 112 and 114 could be operationally
separate from one another or could even conceivably be combined
into one unit performing both of the aforementioned functions. As
mentioned previously, the turntable 108 and all components
propelled by it (including the boom 106 and platform 110) are often
termed the "superstructure".
Preferably, the turntable 108 will include, in one form or another,
a counterweight 116. The concept of a counterweight is generally
well known to those of ordinary skill of the art, as discussed in
the "Background" section of this disclosure. In the illustrated
example, counterweight 116 is a dedicated component that actually
forms a portion of an outer shell of turntable 108. Preferably, the
counterweight 116 will be positioned, with respect to the turntable
108, substantially diametrically opposite the boom 106.
In this respect, FIGS. 2a, 2b and 2c schematically illustrate the
manner in which such a counterweight 116 conventionally acts.
Although a conventional counterweight will act in similar manner
irrespective of the relative circumferential positioning (i.e., the
"swing" or "slew") of boom 106 with respect to chassis 102, FIGS.
2a-2c, in similar manner to FIG. 1, illustrate the boom positioned
at a horizontal angle of 90 degrees with respect to the
longitudinal lie of the lift 100, that is, orthogonal to a
direction that defines the drive direction of the lift 100. The
reason for illustrating the lift 100 in this manner is that, since
this position naturally invites the most unstable configurations
for a boom lift 100 where the dimension (i.e., along the drive
direction) of the lift is greater than the lateral dimension, the
action of counterweight 116 will be better appreciated. Put another
way, this is a typical configuration of maximal instability in that
the boom lies along a horizontally mapped line that itself is
perpendicular to the tipline.
FIG. 2a illustrates the boom 106 in an "intermediate" position, in
this case approximately 40 degrees. On the other hand, FIG. 2b
illustrates the boom being positioned substantially horizontally,
while FIG. 2c illustrates the boom being positioned substantially
vertically.
FIGS. 2b and 2c represent possible extremes of boom elevation,
especially as regards the generation of destabilizing moments. In
practice, a boom angle below the horizontal is quite common.
Accordingly, the two extremes shown in FIGS. 2b and 2c typically
represent the positions in which a typical boom lift will
experience maximum forward and backward instability (as a function
of boom angle), respectively. (Although many boom lifts do not
elevate as far as a vertical angle of 90 degrees, such an angle is
shown in FIG. 2c in order to illustrate an extreme position of
possible backward instability. The notion of a vertical angle of
greater than 90 degrees is not entertained here, as such an angle
could be duplicated by changing the boom's horizontal angle by 180
degrees and fixing the boom at a vertical angle of less than 90
degrees. However, the present invention, in accordance with at
least one presently preferred embodiment, does not in any way
preclude the application of the principles described herein to
vertical boom angles of greater than 90 degrees, and in fact
encourages the possibility of attaining such angles through the
advantage of an increased range of movement that the present
invention is believed to afford, as discussed below.)
With regard to forward instability, as illustrated in FIG. 2b, it
will be noted that a significantly lowered, and extreme outward
positioning of platform 110 will naturally contribute to a maximal
forward destabilizing moment. One benefit of providing the
counterweight 116, then, is to counterbalance this forward
destabilizing moment so as to prevent the lift's center of mass 118
from migrating outside the tipline, which would otherwise result in
forward tipping. It will be appreciated, then, that it is possible
to provide a sufficiently massive counterweight 116 as to
adequately counterbalance the maximal destabilizing moment
experienced in accordance with the configuration shown in FIG. 2b,
and to do so in such a manner as to fulfill any requirements (e.g.,
to account for the presence of one or more individuals on the
platform 110, for the positioning of the entire lift vehicle 100 on
a given slope, and/or for a required margin of safety).
Turning to FIG. 2c, however, it will be appreciated that when the
boom 106 is in a significantly raised or even maximally vertical
position, the risk of significant backward instability will now
present itself. Particularly, given that a counterweight 116 is
provided for the purposes described heretofore, it will now
unfortunately have the opposite effect, that is, of contributing to
instability of the vehicle in a backward direction.
For this reason, it will be appreciated that an appropriate
counterbalance for the counterweight, and one which has been used
conventionally, is the chassis 102 itself. For this reason, it has
been conventional to construct a chassis 102 of such mass as to
adequately counterbalance the destabilizing moment provided in the
backward direction (possibly contributed to by boom 106, platform
110 [possibly with a load thereon] and counterweight 116), to again
prevent the lift's center of mass 118 from migrating outside the
tipline, which would otherwise result in backward tipping.
Although the measures described hereinabove with FIGS. 1-2c have
conventionally been sufficient to reduce the risk of vehicle
tipping in either a forward or a backward direction, concern has
arisen in the industry over the costs associated with providing an
overly massive lift chassis 102. The mass of a lift chassis 102 not
only has ramifications in manufacturing costs, but also in
transport costs as well as other factors, such as the load that
might be applied to fragile surfaces (e.g. mud).
A presently preferred embodiment of the present invention, as best
illustrated (schematically) in FIGS. 3-4c, is believed to help
solve this problem, that is, by maintaining the appropriate
requirements for a boom lift while effectively reducing the overall
mass of a lift structure 100. Preferably, there may be provided a
mechanism or arrangement 120 (see FIG. 3) for effecting the
horizontal movement of at least a portion of turntable 108. This
mechanism 120 may be operatively incorporated with either or both
of the drive arrangements 112 and 114 (which in turn may be
incorporated with one another), in essentially any suitable manner,
in view of t he details provided herebelow.
Accordingly, FIG. 3 is essentially the same view as FIG. 1, but
schematically illustrates, via the horizontal arrows, the fact that
the turntable 108, or at least a portion thereof, may be movable
along a horizontal direction responsive to movement of the boom
106, in a manner to reduce either a forward destabilizing moment or
a backward destabilizing moment, as explained herebelow. As a
consequence of moving the turntable 108 or portion thereof in this
manner, it will be appreciated that an elaborate redistribution of
centers of mass takes place, affecting not only the counterweight
116 but also any other components (e.g., the boom 106) having
centers of mass that might otherwise contribute to destabilizing
movements. Thus, the result of sliding the turntable 108, or
portion thereof, is that the stabilizing moments provided by the
potentially "destabilizing" components are increased.
Thus, FIG. 4a illustrates essentially the same general view as FIG.
2a, but establishes that the turntable 108, or at least that
portion bearing the dedicated counterweight 116, may be in a first
given horizontal position A.
FIG. 4b, on the other h and, illustrating essentially the same
general view as FIG. 2b, shows that the dedicated counterweight 116
has now shifted its horizontal position, thus being disposed more
backwardly than in the case of FIG. 4a, to a position B, thus
counteracting any forward destabilizing moment, both by shifting
the boom and its load to a position closer to the forward tipline
of the lift, and also by moving the mass of counterweight 116
further away from the forward tipline of the lift.
As shown in FIG. 4c, with the boom 106 in a fully vertical
position, or a significantly raised position close thereto, the
slideable portion of turntable 108 has now shifted to a more
forward position C, which has the effect of counteracting (or
neutralizing or reducing) the backward destabilizing moment
contributed to by boom 106 (with load), counterweight 116, and
other components. For this very reason, it is thus possible to
utilize a chassis 102 that is of significantly reduced weight,
since a smaller stabilizing moment will be required.
In one specific prototype tested in the "60-foot" class of boom
lifts, it was possible to reduce the overall weight of the lift by
4920 pounds utilizing the principles discussed above. Particularly,
because of the lengths of moment arms involved, it was found that
highly favorable results were achieved, in that the weight of the
chassis was reduced by 6660 pounds while a dedicated counterweight,
such as the counterweight 116 described and illustrated herein, was
increased by only 1740 pounds, resulting in a net decrease of 4920
pounds for the entire lift structure. Although an increase in the
weight of the counterweight was necessary so as not to compromise
forward stability by reducing the weight of the chassis, the
advantageously longer moment arm of the counterweight in producing
a forward stabilizing moment permitted a much smaller weight for
that purpose than would otherwise be required with a more massive
chassis. Since the boom lift in question weighed 27,780 pounds, the
savings of 4920 pounds resulted in a weight reduction, for the
entire boom lift structure, of about 17.7%.
It is to be understood that the arrangements illustrated and
described with respect to FIGS. 3-4c are provided only as an
example and are in no way meant to restrict the scope of the
present invention. For example, it is conceivable to utilize any
algorithm linking the boom position and the position of the movable
portion of turntable 108 that is deemed to be suitable for the
application at hand. In this respect, it is to be noted that the
present invention need not necessarily be limited to boom lifts.
Other applications of the present invention may be found, for
example, in the context of excavators (including shovel excavators,
jackhammer-type excavators and backhoes), bulldozers, mechanical
shovels (including skid-steer mechanical shovels), mechanical
pincers, tree harvesters, mobile hydraulic cranes (including mobile
hydraulic floor cranes), wheel loaders, tool carriers, boom-mounted
derricks (including boom-mounted hydraulic derricks), oil derricks,
movable and stationary cranes, and other similar machines.
Although an advantage of reduced chassis weight has been described
hereinabove with regard to the provision of a movable turntable
portion as described hereinabove, it should be appreciated that a
corollary advantage may also be enjoyed. Particularly, if the
overall weight of the lift structure 100 is not of particular
concern, then it will be appreciated that a prime advantage
provided by the inventive movable turntable portion is an increased
range of movement of the boom 106. Particularly, for a given fixed
weight of a lift structure 100, it is to be noted that the
inventive movable turntable portion will permit the boom 106 to be
displaced into more extreme positions than in the case of
conventional lifts, since there will be reduced risk of instability
in such extreme positions as compared to conventional arrangements.
Thus, for example, if a conventional lift, possessive of a given
weight, were only capable of displacing the boom up to a vertical
angle of about 75 degrees before compromising any safety
requirements, essentially the same vehicle, possessing essentially
the same mass, but provided with the inventive movable arrangement,
would be able to afford the displacement of the boom to an even
greater vertical angle, possibly 80 degrees or more.
Furthermore, another possible advantage that might be enjoyed in
accordance with at least one presently preferred embodiment of the
present invention is extended horizontal reach. Particularly, it is
believed that the inventive movable arrangement will now permit the
use of telescopic booms (or possibly even articulated booms) that
are longer in reach, and thus more massive, since the additional
moments provided by additional mass in a longer boom, and the
additional moment arm attributed to the work
platform and the load it carries, can be neutralized in view of the
shifting masses described heretofore. Thus, since a longer boom can
now be used, greater horizontal reach can be achieved at all
vertical angles of the boom structure.
It will be appreciated that the present invention need not
necessarily be restricted to a context in which a turntable 108 is
utilized. Indeed, it is possible for the present invention to be
utilized in a context in which there is a vertically pivotable boom
106 but in which its vertical pivot support is fixed with respect
to a circumferential direction. In this manner, it is still
possible to slide a movable portion of the lift back and forth in
response to the position of the boom and still enjoy the benefits
of overall reduced weight.
There are many ways in which a functional interconnection can be
achieved between the movement of the boom 106 and the movement of a
movable turntable portion. Mechanical linkages are, of course,
conceivable, but it is also possible to utilize an electronic
arrangement for communicating an algorithm to a mechanical
interconnection between the boom 106 and the turntable 108. For
example, an appropriately positioned and configured sensor
arrangement could detect the angle of the boom 106 and thence
transmit this information to an appropriately configured drive 120
dedicated to the translational movement of the movable turntable
portion. Based on a predetermined or preprogrammed algorithm, at
least a portion of the turntable 108 could translate in response to
the measured position of the boom 106.
A presently preferred embodiment of the present invention involves
a purely mechanical linkage between a boom and a portion of a
turntable, as discussed herebelow with respect to FIGS. 5-7,
wherein the mechanical linkage actually serves to assert a
positioning algorithm.
FIG. 5 illustrates, in perspective view, components of a boom lift
200 employing a mechanical linkage according to an embodiment of
the present invention. As shown, vehicle chassis 202 may be
supported on four wheels 204 (three of which are shown). Again,
skids, tracks or a fixed arrangement could easily substitute for
wheels 204. A main boom portion 206a of a boom 206 may preferably
be pivot-mounted, at pivot point 206b, on a flange portion 208a of
turntable 208. Flange portion 208a may preferably be so configured
as to provide adequate support for a turntable counterweight.
According to an embodiment of the present invention, a linkage 230
is preferably connected between boom portion 206a and a pivot mount
232. The location of pivot mount 232 will be explained further
below.
In accordance with at least one presently preferred embodiment of
the present invention, turntable 208 may preferably include at
least one slideable portion and at least one non-slideable portion.
The slideable and non-slideable portions will each, of course, be
configured and arranged to rotate with respect to chassis 202.
Accordingly, pivot mount 232 will preferably constitute part of the
non-slideable portion of turntable 208, while turntable flange 208a
will preferably constitute part of the slideable portion of the
turntable.
All turntable components will preferably be configured to rotate
about turntable pivot 236, particularly about rotational axis 238
(see FIG. 6). Also shown in FIG. 5 are rails 239 of turntable 208.
These components will be better appreciated and understood with
regard to the views shown in FIGS. 6 and 7.
Accordingly, FIG. 6 is a side view of essentially the same
components shown in FIG. 5, but with sore additions. Indicated at
240 is a lift cylinder that is pivot-mounted at pivot point 244 on
turntable flange 208a, while also being pivot-mounted, at pivot
mount 246, with respect to boom portion 206a. Thus, it will be
appreciated that, whereas link 230 extends between boom portion
206a and a non-slideable portion (232) of turntable 208, lift
cylinder 240 extends between boom portion 206a and a slideable
portion (208a) of turntable 208. Accordingly, it will be
appreciated that, upon movement of lift cylinder 240 to either
raise or lower the boom portion 206a, a sliding displacement of all
slideable portions of turntable 208 (including flange 208a) will
occur.
In FIG. 6, the boom portion 206a is in a lowermost, or "stowed"
position. However, in FIG. 7, boom portion 206a is shown as being
in a significantly raised position. The relative sliding
displacement that has taken place in the interim can best be
appreciated by comparing the relative positions of rotational axis
238 and rails 239 in both of the FIGS. 6 and 7. Thus, it will be
appreciated that the length of mechanical link 230, as well as the
position of the connecting pivot points 232 and 233, will, along
with the dimensions and connection points of lift cylinder 240,
govern the manner in which the slideable portion of turntable 208
slides with respect to both the chassis 202 and the non-slideable
portion of turntable 208.
An algorithm that has been found to be highly effective and that
might be utilized, in accordance with a preferred embodiment of the
present invention, in conjunction with the mechanical linkage
described and illustrated with respect to FIGS. 5-7, may be
expressed by way of the following equation: ##EQU1## where:
d:translational displacement
.theta.:boom vertical angle
d.sub.0 :translational displacement for .theta.=0
x.sub.0 :horizontal distance between boom pivot and link lower
pivot
y.sub.0 :vertical distance between boom pivot and link lower
pivot
l:link length between pivots
r:distance between boom pivot and link upper pivot
.psi.:angle between horizontal and line that passes through boom
pivot and link upper pivot
Additionally, Table I provides data obtained with a prototype lift
in accordance with an embodiment of the present invention,
illustrating the sliding (or translational) distance undertaken by
a movable turntable portion for given lift angles of a boom:
TABLE I ______________________________________ Boom Angle
Translation Distance (Degrees) (inches)
______________________________________ -15 0.00 -14 -0.03 -12 -0.04
-10 -0.03 -8 0.00 -6 0.07 -4 0.16 -2 0.28 0 0.43 2 0.61 4 0.81 6
1.05 8 1.31 10 1.60 12 1.91 14 2.26 16 2.63 18 3.02 20 3.45 22 3.90
24 4.37 26 4.87 28 5.39 30 5.94 32 6.50 34 7.09 36 7.70 38 8.33 40
8.98 42 9.65 44 10.33 46 11.03 48 11.74 50 12.46 52 13.20 54 13.95
56 14.70 58 15.46 60 16.23 62 17.00 64 17.78 66 18.56 68 19.34 70
20.11 72 20.89 74 21.66 75 22.04
______________________________________
Generally, it is to be understood that any algorithm that might be
used for governing the interrelationship between one characteristic
of the lift, such as boom angle, to another characteristic, such as
the horizontal position of the slideable portion 208a of turntable
208, may be tailored to the machine in question, depending upon the
needs of the user. To this end, then, it is possible to alter the
dimensions, orientation or positioning of a mechanical link, such
as link 230, to assert the algorithm desired.
It is also conceivable, within the scope of the present invention,
to utilize a mechanical linkage that is not a fixed link. As one
example, it might be possible to replace the mechanical link 230
discussed heretofore with a hydraulic cylinder or any other
conceivable type of variable-length link. Additionally or
alternatively, it is possible to utilize a link that disengages or
engages (i.e., becomes effective) only when certain conditions are
met. Thus, it is conceivable to utilize a link that will
interconnect, for example, a portion of a boom and a portion of a
turntable or superstructure over a given range of boom angles but
will disengage over a different range of boom angles. Any of
several different possible arrangements could be used in this
manner.
It is to be understood that the present invention is not meant to
be restricted to the concept of shifting a turntable portion merely
in response to the boom angle. In fact, it is conceivable to shift
a counterweight in response to essentially any movement of a boom,
such as strictly circumferential movement or a combination of
vertical and circumferential movement. In this vein, it will be
appreciated that, on a typical boom lift, in which a chassis does
not exhibit complete rotational symmetry of mass, it is conceivable
to shift a counterweight as a function of circumferential position
of the boom in order to compensate for variations in instability
that occur as a function of the circumferential position of a boom.
The present invention broadly contemplates any possible types of
mechanical linkage that might be used for this purpose, although it
would appear that an electronic input to a mechanical linkage would
be particularly wellsuited for this purpose.
It is conceivable, within the scope of the present invention, to
shift the position of a boom in response to changing boom
conditions, rather than, or in addition to, shifting a
counterweight or movable turntable portion. As one possible example
of this, it is conceivable to provide two or more different
mechanical linkages with the effect of configuring two or more
discrete objects to move at two different rates or in accordance
with two different algorithms. Of course, it will be appreciated
that i n the preferred embodiment of the present invention
described heretofore, the boom 206 actually moves along with the
sliding portion 208a of turntable 208 as part of an elaborate and
highly effective redistribution of various masses on the boom lift
200.
In at least one presently preferred embodiment of the present
invention, it will be appreciated that a suitably arranged
mechanical linkage can assert a one-to-one correspondence between
the vertical angle of the main boom portion 206a and the horizontal
position of the turntable. In other words, the mechanical linkage
can assert one and only one possible horizontal position of the
slideable turntable portion 208a for each possible boom angle. In
this vein, the one-to-one correspondence need not necessarily be
linear. However, it is conceivable to provide a mechanical, and
certainly electronic, linkage that does not necessarily effect a
one-to-one correspondence. Particularly, it is conceivable to
create a mechanical or electronic linkage that ensures that, for
example, for a given lower range of vertical angles, the movable
turntable portion 208a will not displace horizontally at all, but
will only do so beyond a given threshold angle.
It is to be appreciated that the relationship between the vertical
angle and the horizontal position of the turntable could be linear
or non-linear. In the specific algorithmic example described
heretofore, it will be noted that there is a cosine relationship
between the two variables. Thus, essentially any arrangement for
asserting a positional relationship between the boom position and
the movable turntable portion position is conceivable within the
scope of the present invention.
It will be appreciated that, although the specific embodiments
illustrated herein involve the use of only a simple single boom
(e.g., a telescoping single boom), the same principles can be
applied in conjunction with an articulated boom, as is often found
in the industry. It is conceivable to peg the movement of the
movable turntable portion 208a to the movement of any portion of a
multi-segmented boom, and it need not necessarily be the "tower"
segment (i.e., that segment that extends from the chassis or other
main structure) Furthermore, movement of the movable turntable
position could be governed by the composite movement of different
segments of an articulated boom, according to a predetermined
algorithm that is asserted either mechanically or electronically.
However, in at least one present preferred embodiment of the
present invention, it will be noted that the governing factor for
dictating the position of the movable turntable portion, is what
may be termed the "lift angle" of the boom, or that vertical angle
formed by the main segment of the boom, extending from the chassis
or other main frame, with respect to the horizontal.
If any electronic input to a mechanical linkage is utilized, it
will be appreciated that there are several manners in which an
algorithm can be effected. A look-up table is one possibility. FIG.
8 illustrates an example.
Thus, in accordance with an alternative embodiment of the present
invention, FIG. 8 illustrates a pivotable boom portion 306a mounted
on a movable turntable portion 308a. Indicated at 350 is a mounting
block from which a hydraulic cylinder 352 extends to be connected
to movable turntable portion 308a. Preferably, movable turntable
portion 308a will be so mounted and configured as to be capable of
sliding in response to extension of cylinder 352.
A sensor 354 may be provided at the pivot point between boom
portion 306a and movable turntable portion 308a, for the purpose of
reporting to microprocessor 356 a physical parameter (e.g., the
lift angle) relating to boom portion 306a. Microprocessor 356,
conceivably containing a lookup table or algorithm for this
purpose, may then transmit to a hydraulic valve 358 a signal that
urges a given action of hydraulic valve 358 as a function of the
position of boom portion 306a, to consequently cause cylinder 352
to retract or extend and thus reposition movable turntable portion
308a.
It is also conceivable to utilize a hybrid mechanical and
electronic linkage in order to peg the movement of a movable
turntable portion to that of a boom. As one possible example, a
"gross" pattern of motion could be asserted by a mechanical
linkage, to be followed up by a "fine-tuning" of the positional
relationship by way of an electronic input to a
mechanical linkage. In another possible example, a mechanical
linkage could be used to assert a positional relationship over a
given range of boom angles or other physical values, only to be
replaced by an electronic input to a mechanical linkage over
another range of angles or other physical values.
It is conceivable, within the scope of the present invention, to
govern the position of the movable turntable portion with regard to
factors associated with the boom other than the position of the
boom. For instance, it is possible to use the personnel or material
weight present on the platform as a factor for determining the
position of the movable turntable portion. For instance, it is
possible to measure the load present on the platform and then alter
the position of the movable turntable portion accordingly in order
to maintain adequate stability.
To carry out such an embodiment, for example, it is conceivable to
utilize weight sensors appropriately positioned on the platform to
transmit data back to an electronic input mechanism (for a
controlling mechanical linkage). The result could be an
instantaneous redefinition of the permissible "envelope" within
which the lift is able to operate. Such an arrangement, of course,
could be utilized by itself in governing the position of the
movable turntable portion or could be used in addition to any
arrangement in which the movable turntable portion position is
controlled by position of the boom. For example, in addition to
altering the position of the movable turntable portion based on the
load applied to the work platform, the position of the movable
turntable portion could also be altered as a function of the lift
angle of the boom and/or of the degree that one or more portions of
the boom telescopes.
Also, when the concept is discussed herein of controlling the
position of the counterweight via the position of the boom, it is
to be understood that this covers a very wide range of concepts.
Particularly, it will be noted that many booms involve movable
components that move independently of the action of the main boom
and are thus independent of the vertical angle of the main boom.
Such components include, but are not limited to, for example,
rotatable platforms, telescoping platforms, segmented booms, etc.
In such instances, movement of the movable turntable portion could
conceivably govern by, at least in part, the movement of such
components. For example, if a platform is extendible with respect
to the main boom segment or segments, its position could
conceivably be utilized as a factor in determining the position of
the movable turntable portion. A mechanical or electronic linkage
could be provided to ensure such governance. It is conceivable to
govern the position of the movable turntable portion on the basis
of only one such factor or on several such factors, any or all of
which could be utilized in combination with the concept of
governing the position of the movable turntable portion on the
basis of the position of a main or primary boom segment, such as
that segment which is pivoted directly on the chassis or other main
frame. Accordingly, it will be appreciated that the present
invention, in accordance with at least one presently preferred
embodiment, broadly contemplates essentially any arrangement in
which a stabilizing moment is imparted to a lift-type structure on
the basis of at least one state of at least a portion of the
boom.
It will also be appreciated that the present invention contemplates
essentially any arrangement in which a stabilizing moment is
imparted to a lift. In this manner, it is possible to provide an
arrangement in which there is not a dedicated counterweight
imparting a stabilizing moment, but some other means for doing so.
As one possible example, there could exist one or more fluid tanks
on the boom lift 200, and a transfer of mass could take place by
redistributing the fluid among different portions of the lift. In
principle, it will be appreciated that such a redistribution of
fluid can be regarded as being essentially analogous to the sliding
action of a movable turntable portion, as discussed heretofore.
Although the present invention may be utilized in a wide variety of
contexts, its advantages may be appreciated, in non-restrictive
fashion, with respect to a boom lift structure. As discussed
previously, it has been found, for example, that a prototype boom
lift structure employing a "sliding turntable portion" design as
described and illustrated hereinabove, could represent a savings in
weight of about 18% in the lift as compared to a conventional
arrangement in which no portion of the turntable is able to
slide.
It is conceivable, within the scope of the present invention, to
apply the general principles discussed herein to essentially any
type of load carrier, such as a vehicle. Particularly, the present
invention, in accordance with at least one presently preferred
embodiment, contemplates a load carrier having a load bearing
portion and an arrangement for imparting to the load carrier a
stabilizing force, based on at least on state of the load-bearing
portion, for averting destabilization of the load carrier.
Furthermore, the present invention, in accordance with at least one
presently preferred embodiment, broadly contemplates a load carrier
including an arrangement for responsively redistributing mass based
on at least one state of at least a portion of the load carrier.
Such responsive redistributing could, for example, be carried out
instantaneously, virtually instantaneously, or in a matter of very
little time.
Additionally, the present invention, in accordance with at least
one presently preferred embodiment, broadly contemplates a load
carrier including an arrangement for automatically redistributing
mass based on at least one state of at least a portion of the load
carrier. Such automatic redistributing could be carried out by
essentially any conceivable means.
It is to be understood that the present invention, in accordance
with a t least one presently preferred embodiment, may find
application s in a wide variety of contexts, many of which have
been mentioned and described heretofore. An oil derrick would
appear to be a pertinent example in this regard, since the
structural supports tend to be firmly anchored in a solid
surface.
In such contexts (i.e., oil derricks and other stationary
arrangements), the present invention, in accordance with at least
one presently preferred embodiment, could be employed to reduce
structural loading on the stationary frame being employed, which
would essentially be analogous to counteracting destabilizing
moments on a lift having supports (e.g., wheels or free stationary
members) that are not fixed.
If not otherwise stated herein, it may be assumed that all
components and/or processes described heretofore may, if
appropriate, be considered to be interchangeable with similar
components and/or processes disclosed elsewhere in the
specification, unless an express indication is made to the
contrary.
If not otherwise stated herein, any and all patents, patent
publications, articles and other printed publications discussed or
mentioned herein are hereby incorporated by reference as if set
forth in their entirety herein.
It should be appreciated that the apparatus and method of the
present invention may be configured and conducted as appropriate
for any context at hand. The embodiments described above are to be
considered in all respects only as illustrative and not
restrictive. The scope of the invention is defined by the following
claims rather than the foregoing description. All changes which
come within the meaning and range of equivalency of the claims are
to be embraced within their scope.
* * * * *